DMA requests from at least one DMA channel with a higher priority than the floppy-disk
controller are disabled for at least a portion of a write to floppy DMA operation
that includes the transfer of the last byte. This helps ensure that DMA requests
generated by the floppy-disk controller will be responded to in under 14 S
preventing an undetected underrun condition on systems with flawed floppy disk
controllers from occurring. An estimate of when the last byte of a write to floppy
DMA operation is going to be transferred is made. This estimate may be based upon
a fixed interval from the start of the write operation. This estimate may also
be based upon readings taken from the byte counter and of the DMA controller and
the system timer.
